"An Introduction Of Knitting Machines"

Types of Knitting Machines---

1. Circular Knitting Machine

                         These are two types:--- 

•  Single Jersey  Knitting Machine
•  Double Jersey  Knitting Machine: 

                       These are two types---

                                            (a) Rib
                                            (b) Interlock   

2. Flat Knitting Machine.

Some images of these machines---

Single Jersey Circular Knitting Machine

Double jersey circular knitting machine(Rib & Interlock Type)

V-bed knitting machine

V-bed knitting machine(Top View)

Antique Sock Circular Knitting Machine

Antique Sock Circular Knitting Machine(Close View)

"An Introduction To Knitting Technology"

 

What is Knitting?

Knitting is a method by which thread or yarn may be turned into cloth or other fine crafts. Knitted fabric consists of consecutive loops, called stitches. As each row progresses, a new loop is pulled through an existing loop. The active stitches are held on a needle until another loop can be passed through them. This process eventually results in a final product, often a garment.

figure 1 : type of knitting to produce a loop

Type of Knitting Stitches

In textile knitting, there are two types of stitch used by the manufacturer to produce a knitted product ; Warp Knitted and Weft Knitted stitches. Each of them have different properties in terms of advantages & disadvantages, and also the ways of production process.

Weft Knit Stitches

It is the most common types used by the manufacturer in produce textile knitted products such as Shirts and Socks. In terms of colour patterning, weft knit may be knitted with multiple yarns to produce interesting pattern design. There are few types or technique to produce weft knit structure, Single jersey, Purl, and Rib are some of the technique that been used to produce weft knitted structure.

figure 2 : Properties of warp knit fabric and weft knit fabric

Types of Machine Used by Weft Knit

figure 3 ; Type of knitting machine

There are two kind of machines used by the manufacturer to produce weft knit, Flat Knitting Machine and Circular Knitting Machine. Each of these machine can only produce different kind of products specifically. For Flat Knitting Machine, a V-bed type of machine may be use for knitting to produce design by using the facilities of rib loop transfer and needle backing. While for Circular Knitting Machine, the needle will be arranged on circumference of needle bed.

figure 4 : structure fabric in flat bed machine and circular knitting machine

Circular Versus Flat Knitting Machine

• Production : Circular is much more productive than Flat Knitting Machine
• Patterning : Circular is less pattern design because of the restricted patterning abilities
• Fabric take-down : Fabric produce from Circular can’t be driven directly

Warp Knit Stitches 

Warp knitted is produced from a set of warp yarn. It is parallely knitted to each other down the length of the fabric. Since knitted fabric may have hundreds of wales, warp knitted is typically done by machine.[1]

figure 5 : Techniques or types of Warp Knitted Structure

Properties of Warp Knitted Structure

In production, there will be two types of guide bar may be choose to produce knitted product.

• Single Guide Bar : Low strength, Lack of stability, Poor of covering power, and loop inclination
• Double Guide Bar : Good dimensional stability, Reasonal cover, and Better loop and Shape[2]

Warp knitting  are divided by two,that are overlap and under lap

figure 6: meaning of warp knitting and type of warp knitted loop

SUMMARY

The popularity of knitting has grown a lot within the recent years owing to the adaptability of various man-made fibers, the increased versality of knitting techniques and the growth in demand for wrinkle-resistant, stretchable, snug-fitting fabrics.

Knitted textiles and apparel represent approximately one third of the global textile market, together with the advances of new technical applications for knitted textiles. Lets we talk about the new advancement of knitting technology in textile world.[3]

• Wholegarment’ technology – this advance in knitting technology by developing the slide needle.  The slide needle resulted from research into the latch needle and the knitting process.  The needle consists of a hook located centrally between a flexible two-piece slider mechanism.  Stitches are transferred by the sliders during the knitting process.It provide greater comfort than cut and sew clothes.
• digital injet printing-  Designs can be transferred directly from a computer and printed onto fabric in almost the same way as a word-processed document is printed onto paper.[4]

References:

[1] Lecturer’s note, by Miss Eryna Binti Nasir Knitting

[2] Courtesy: Jimmy K.C. Lam, The Hong Kong Polytechnic University

[3] Billie J. Collier, University of Tennessee & Phyllis G. Tortora, Queens College. Understanding Textiles, (Sixth Edition).

[4] http://www.knittingtogether.org.uk

"Some images of machines used in spinning of yarn"

Sequence of machines used in spinning section-- 

1.Blow room:-

• Bale plucker,

• Bale opener,

• Pre-cleaner,

• Mixer,

• Fine cleaner,

• Lap former,

2. Carding machine.

3. Draw frame.

4. Simplex machine.

5. Ring Frame.

6. Rotor spinning machine

7. Winding machine:-

• Cone winding machine

• Cheese winding machine.

 Blow room

Blow room

Bale Opener

Lap Former

Carding Machine

Draw Frame

Simplex/Speed Frame/Roving Frame

Ring Frame

Rotor spinning Machine

Cone Winding Machine

Cheese Winding Machine

"Weaving on the loom"

                                                        

LOOM: A machine for weaving fabric by interlacing a series of vertical, parallel threads (the warp) with a series of horizontal, parallel threads (the weft/filling). The warp yarns from a beam pass through the heddles and reed, and the filling is shot through the “shed” of warp threads by means of a shuttle or other device and is settled in place by the reed and lay. The woven fabric is then wound on a cloth beam.
The major components of the loom are the warp beam, heddles, harnesses, shuttle, reed and takeup roll. In the loom, yarn processing includes shedding, picking, battening and taking-up operations.

The principal elements of any type of loom are the shedding, picking, and beating-up devices.

• Shedding. Shedding is the raising of the warp yarns to form a hed through which the filling yarn, can be inserted. The shed is the vertical space between the raised and unraised warp yarns. On the modern loom, simple and intricate shedding operations are performed automatically by the heddle or heald frame, also known as a harness. This is a rectangular frame to which a series of wires, called heddles or healds, are attached. The yarns are passed through the eye holes of the heddles, which hang vertically from the harnesses. The weave pattern determines which harness controls which warp yarns, and the number of harnesses used depends on the complexity of the weave. Two common methods of controlling the heddles are dobbies and a Jacquard Head.

Dobby Shedding System:
The dobby shedding motion of the warp ends is created by the movement of the heald frames. The maximum practical number of harness frames in terry weaving machines with dobby is 20. Dobby looms can produce weaves in limited numbers and limited designs. The difference of this system from the other traditional dobby looms is that the motion of the pile and ground warps is transferred separately. There are also systems in which the pile warps are given shedding motion by dobby and the ground warp ends by cam

Jacquard Shedding System:

Each warp end is controlled through a separate motion. Very different and very complex structures can be woven. In terry fabric it is the pile warp which shows the design. The ground warp ends are woven 2/1 ribs (most commonly), 2/2 ribs, 1/1 plain weave and 3/3 ribs (the rarest) As these weaves do not require a jacquard shedding system, in some weaving machines, the pile warp ends take the shedding motion from the jacquard system whereas the ground warp ends take from the cam. Jacquard machines may either work in a traditional mechanical system with the help of needles and design cards or a contemporary electronic system which works through electronic transmitting elements with design files and electronic. The pile warp ends are looser than input. The pile warp ends are looser than ground pile ends, thus the shedding of the pile weft ends must be wider than that of ground warps. Otherwise, contact may occur between the pile warp ends and the pick carrying device, which may cause high numbers of end breakages. A wider shed also improves the loop formation. Pile tension rod should guide the pile warp ends from the position which has the same level with the center of the shed. With this, the pile warp ends in the upper and in the lower shed will maintain the same tension. Thus, the pile loops on both sides of the fabric will have the same length.

• Picking. As the harnesses raise the heddles or healds, which raise the warp yarns, the shed is created. The filling yarn in inserted through the shed by a small carrier device called a shuttle or by other methods described below.

Types of Picking Mechanism

Picking mechanisms are classified into two main types. These are :

1. Conventional picking mechanism or negative picking mechanism
2. Unconventional picking mechanism or positive picking mechanism

 Conventional Picking Mechanism or Negative Picking Mechanism

In this mechanism, a carrier known as shuttle carries the weft yarn in a package called the “pirn”.

Picking through the open shed

Figure indicates the insertion of weft yarn by passing the shuttle through the warp shed.

Unconventional Picking Mechanism or Positive Picking Mechanism

In this mechanism, the weft yarn is inserted through the warp shed directly or positively by air, water, a projectile, a rapier or a needle. These mechanisms are therefore known as “positive picking mechanisms”. Looms which do not use shuttles for weft insertion are known as “shuttleless looms”.

• Beating. As the shuttle moves across the loom laying down the fill yarn, it also passes through openings in another frame called a reed (which resembles a comb). With each picking operation, the reed presses or battens each filling yarn against the portion of the fabric that has already been formed. The point where the fabric is formed is called the fell.

Classification Of Loom

Loom may be classified into two basic types with respect to picking medium,

1. Shuttle loom
2. Shuttleless loom

Shuttle Loom
The term Shuttle loom refers to any loom that uses a shuttle. 

Shuttle is a boat-shaped device, usually made of wood with a metal tip that carries filling yarns through the shed in the weaving process. It is the most common weft-insertion device. The shuttle holds a quill, or pirn, on which the filling yarn is wound. It is equipped with an eyelet at one end to control rate. The filling yarn is furnished during the weaving operation.

Shuttle

Shuttleless Loom
A loom in which some device other then a shuttle is used for weft insertion, Shuttleless loom is further classified into follows:

1. Projectile loom
2. Rapier loom
3. Air jet loom
4. Water jet loom

Projectile Loom
A shuttleless loom that uses small metal devices i-e a bullet-like projectiles to carry the filling yarn through the shed. Fill is inserted from the same side of the loom for each pick. A tucked selvage is formed.

The mechanism of weft insertion is as follow:

          A - Warp shed
B - Weft
        C - Projectile

Rapier Loom
Looms in which either a double or single rapier (thin metallic shaft with a yarn gripping device) carries the filament through the shed. In a single rapier machine, the yarn is carried completely across the fabric by the rapier. In the double machine, the yarn is passed from 

one rapier to the other in the middle of the shed.

Structure of rapier loom 

Weft insertion mechanism of rapier loom

          A - Warp shed
B - Weft
     C - Rapier

Air jet Loom
A loom that employs a jet of air to carry the filling yarn through the shed.

Air-Jet Loom mechanism

Air-Jet weft insertion

Water jet Loom
A loom that employs a jet of water to carry the filling yarn through the shed

"An Introduction To printing styles"

Introduction:

Printing: Printing could be referred to as a sort of selective dyeing that makes an important contribution fabric decoration thanks to the combination of colors and dyeing methods.

Printing involves localized coloration. This is usually achieved by applying thickened paste containing dyes or pigments onto a fabric surface according to a given color design. In particular, the viscosity of print paste is critical. It determines the volume of paste transferred to the fabric and the degree to which it spreads on and the surface yarns.

Printing was originally done by hand using wooden blocks with a raised printing surface, much as children do potato printing.

Printing styles:

Style refers to the manner by which a particular action is performed. Styles of printing mean the manner in which a printed effect is produced.

The different styles of printing are-

•  Direct style of printing.
•  Discharge style of printing.
•  Resist style of printing.
•  Flock style of printing.
•  Burn out or Devore style of printing.
•  Crepon or crimp style of printing.

In broad sense the styles of printing are classified as-

1.      Direct style printing

2.      Discharge style printing

a.      White discharge

b.      Color discharge

3.      Resist style printing

a.      White resist

b.      Color resist

1. Direct style of printing:

In this style the dyes are applied directly at the required places of the fabric, leaving the other portion white, by any printing method like block printing, screen printing etc. so this style is called direct style of printing.  

Direct style involves transfer of paste containing dyes to the appropriate areas of the fabric. After drying the required localized dyeing of the fibers occurs during steaming. Washing follows to remove the paste residue. In case of pigment printing the pigments adhere to fabric surface with the cured binder film. No additional treatment is needed.  

Direct printing is the most important type of printing. It may even take place on a uniformly dyed fabric to produce particular color effect. Such over printing produces are called ‘fall on ‘effects.

Advantages: 

• It is the easiest printing style to operate.
• Least expensive.
• Suitable for the printing of both simple and complicated design and
•  Color matching with the original design sketch is easy.

2. Discharge style of printing:

Discharge means removal and discharging system means the process which can produce a white or colored effect on a previously dyed ground.

This discharging of color from previously dyed ground is carried out by a discharging agent which is actually a oxidizing and reducing agent capable of destroying color by oxidation and reduction.

The discharging agent’s are-

a.       Oxidizing agent: Potassium chlorate, Na-chlorate

b.      Reducing agent: Rongalite-c, Stannous chloride

Discharge printing is a method where a dyed fabric is printed with discharging agents which selectively destroy the dye. A white discharge is produced.

An alternative method is to print along with discharging agent, non dischargeable dye which gives a colored discharged surrounded by a ground color.

There are two types of discharge style printing such as-

a. White discharge

After dyeing and printing the discharging agent discharges the dye of printed area and leaves the dye of unprinted areas unaffected. So a design is produced on the color ground.

b. Color discharge:

    

 Dye stuff which is strongly resistant to discharging agent are included in the printing paste along with discharging agent.  The discharging agent of print paste discharges the color at the printed area. At the same time the dye stuff of print paste deposits and fixes itself on the ground. As a result of color discharge effect is obtained. In this way one or more colors may be applied.

Advantages:

•  Large areas of ground of ground color are possible.
• Delicate colors and intricate patterns possible on deep ground color, excellent depth and clarity possible.
•  Higher production cost but long lasting unique styles.

3. Resist style printing:

 Resists means to hinder. In this process a chemical is applied to the fabric that will prevent the fixation of any coloring agent employed afterwards on that area.

It is one of the oldest printing style in which two resulting pattern can be obtained.

In resist printing the fabric is first printed with an agent that resists either dye penetration or dye fixation. During subsequent dyeing, only the areas free of the resist agent are colored.  

There are two types of resist printing such as-  

         

 White resist: if no color is added in the printing paste solution along with resist salt, after dyeing the printed areas remains white. This is called white resist.

        

 Color resist: if any coloring material is added in the print paste along with resist salt, after dyeing the printed areas contain the color added to print paste and the remaining areas will contain the color of the dye solution. As a result colored resist effect is obtained.

   

Advantages:

a.      can use white or colored resist

b.      can use dyes of much higher stability than those used in discharge printing & therefore much higher fastness can be obtained.

c.       Non dischargeable dyes can be used for the ground color.

4. Flock style of printing:

 Flock printing is a process in which a flock is fixed onto a cloth by means of adhesive to form printed pattern. It produces a pile or velvet effect on the fabric similar to form a printed pattern.

 Flock is branch of short fiber. In the electrostatic method of flocking the fabric is printed with an adhesive and passes on a moving belt through an electric charge. The flock made from cotton, rayon and synthetic is filtered from the flock hopper on to the fabric and is attracted to the adhesive in perpendicular form. After a backing process the sharp less fiber s are removed. 

5. Burn out or Devore style of printing.  

Burn-out printing is also called Transparence process, Corrosion Process or Carbonization Printing (in Japan). Being printed by the printing paste which is mixed by a kind of chemical. After proper process, one of the fibers in the fabric will be destroyed. Then it comes into being a burn-out fabric of a particular and translucent style.

The production of burn-out printing has a transparent and a concavo-convex feeling. With a natural printing pattern and unique style, it just looks like the organdie which is half transparent, colorful and shiny.

6. Crepon or crimp style of printing:

This style is characterized by the appearance of alternate plain and crinkle stripes in the fabric itself. This effect can be brought about by localized fabric shrinkage with appropriate swelling agent.

              

For example, if cotton fabric is printed in a striped pattern with strong caustic soda, it shrinks in the printed areas and thus causes the unprinted areas to crimp. The greater the shrinkage or contraction of the printed areas, the more pronounced the effect becomes.

  

Conclusion:

Printing, like dyeing, is a process to applying color to a substrate.however instead of coloring the whole substrate as in dyeing; print color is applied only to defined areas to obtain the desired pattern. This involves different techniques and different machineries with respect to dyeing, but the physical and chemical processes that take place between the dye and the fiber are analogous to dyeing.